San Francisco, Sep 2 (DPA) The daughters of kidnap victim Jaycee Dugard thought she was their sister and were never told she was abducted by their father when she was 11, a Dugard family representative said Tuesday.

'Jaycee had to explain to them, like two days ago, that she had been kidnapped. They didn't even know that,' Dugard's stepfather, Carl Probyn, told broadcaster ABC. 'They are upset about this, because that's their father and he's in jail.'

Dugard and her daughters, 11 and 15, were reunited with her family last week and are undergoing close psychological counselling as they try to adjust to freedom.

Dugard was kidnapped at age 11 in 1991 and kept in isolation for 18 years. Police say she was repeatedly raped by her captor and bore him two daughters. Phillip Garrido, 58, and his wife, Nancy, 54, pleaded not guilty Friday to 28 charges of kidnapping, rape and conspiracy.

'It's step by step, it's like being on Mars,' said Probyn.